title: Diacylglycerol promotes GLUT4 translocation to the cell surface in a PKCε-dependent and PKCλ/ι and -ζ-independent manner.
abstract: OBJECTIVE
  Emerging evidence has pointed to the participation of protein kinase C (PKC) in insulin-regulated trafficking of the glucose transporter GLUT4. The present study investigated the effect of the PKC activator diacylglycerol (DAG) on GLUT4 trafficking and glucose uptake.
  
  
  METHODS
  3T3L1-GLUT4myc fibroblast cells expressing GLUT4myc were differentiated into adipocytes. Western blotting, glucose assay, and real-time RT-PCR were carried out in 3T3L1-GLUT4myc adipocytes. PKCλ/ι, -ζ, -ε, and -γ were knocked-down by transfecting each siRNA. Activity of PKC isozymes was assayed under the cell-free conditions.
  
  
  RESULTS
  Insulin increased cell surface localization of GLUT4 in 3T3L1-GLUT4myc adipocytes, and a similar effect was obtained with 1,2-dioleoyl-sn-glycerol (DO-DAG), 1-oleoyl-2-acetyl-sn-glycerol (OA-DAG), or 1,2-dipalmitoyl-sn-glycerol (DP-DAG). Like insulin, DO-DAG stimulated glucose uptake into adipocytes, but no significant synergistic increase in the glucose uptake was found with co-treatment with insulin and DO-DAG. Insulin activated Akt in adipocytes, but no Akt activation was induced by any investigated DAG. In the cell-free PKC assay, DAGs examined here activated PKCα, -βI, -βII, -γ, -δ, and -ε, but the atypical PKC isozymes PKCλ/ι and -ζ were not activated. Insulin-induced GLUT4 translocation to the cell surface was inhibited by knocking-down PKCλ/ι and -ζ, but not PKCγ or -ε. In contrast, DO-DAG-induced GLUT4 translocation to the cell surface was clearly prevented by knocking-down PKCε.
  
  
  CONCLUSIONS
  The results of the present study indicate that DAG stimulates GLUT4 translocation to the cell surface by activating PKCε, regardless of PKCλ/-ι and -ζ.
authors.affiliation: Division of Bioinformation, Department of Physiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya 663-8501, Japan. ayako-t@hyo-med.ac.jp
authors.forename: Ayako
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kanno
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Nishizaki
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D004075:Diglycerides / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000502:physiology*; D051379:Mice; D011493:Protein Kinase C / Q000502:physiology*; D051744:Protein Kinase C-epsilon / Q000502:physiology*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta
chemical_list: D004075:Diglycerides; D051275:Glucose Transporter Type 4; D007527:Isoenzymes; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta; C495693:Slc2a4 protein, mouse
keywords: Diacylglycerol; GLUT4; Protein kinase C; Trafficking